The Secretory Process and Yeast Cell-surface Assembly

Abstract

INTRODUCTION
The goal of this paper is to review our knowledge of macromolecular secretion in Saccharomyces cerevisiae in terms of the synthesis and movement of exported proteins and carbohydrates, the membrane organelles that participate in this process, and the contribution that parts of this process make to the localization of organelle-associated proteins. Some of the material presented in this paper has been reviewed recently (Cabib 1975; Farkaš 1979; Byers 1981), and the chapters in this volume by Ballou, Henry, and Cooper are pertinent.

The mechanism of budding growth is relevant to this discussion. During most of the division cycle, cell-surface growth is restricted to the bud. Membrane enzymes, such as glucan synthetase, are responsible for much of this localized growth, and yet the plasma membrane is continuous and surrounds both the bud and mother portions of the cell. Thus, budding growth implies some mechanism for membrane differentiation and localization of surface components. Our attention has also been drawn by the connection between surface growth and secretion. These processes coincide temporally and spatially in a budding cell. We will present the evidence that supports a role for the secretory process in the formation of a bud.

It is tempting, though risky, to draw on principles derived from studies of other secretory processes. This paper includes some analogies and speculations that we hope will stimulate interest in yeast as a simple system for the study of eukaryotic secretion and cell-surface growth. Unfortunately, yeast has not been a popular source material for the...